Hi there,
I want to report a segfault in DiGraph.automorphism_group.
> On my machine the following code creates a segfault if
> finite_semigroup-nt.patch is applied and works if not.
>
> sage: G = DiGraph()
> sage: G.add_vertices([1, 6, 9])
> sage: G.add_edges([(9, 1, None), (9, 6, None)])
> sage: G.automorphism_group()
> ****BBBBOOOOMMMM****
>
> Can someone confirm that the segfault happen on other machine ?
>
> For Nicolas: could it be related to the recent work on categories ?
We (Nicolas & myself) tracked back the segfault and found that it was
triggered by the category system but it should have nothing to do with it. The
problem seems to been raised by an early import of DiGraph.
Here is a simple way to trigger the segfault:
Starts from vanilla sage-4.7.2 together with the following patch:
"""
# HG changeset patch
# Parent 9e29a3d84c48c399daaf3920bcb8b17273a0e876
diff --git a/sage/categories/all.py b/sage/categories/all.py
--- a/sage/categories/all.py
+++ b/sage/categories/all.py
@@ -39,6 +39,8 @@ from finite_monoids import FiniteMonoids
from finite_groups import FiniteGroups
from finite_permutation_groups import FinitePermutationGroups
+from sage.graphs.digraph import DiGraph
+
# fields
from number_fields import NumberFields
"""
Then,
sage: DiGraph().automorphism_group()
Kaboom !!!
I don't think I'll have time to investigate this further. Should I open a
ticket ?
Cheers,
Florent
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